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  • 51.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Dynamic excitation and higher bending modes for prediction oftimber bending strength2010In: Proceedings of the final conference of COST action E53, 2010Conference paper (Other academic)
    Abstract [en]

    The potential of utilizing eigenfrequencies corresponding to edgewise bending modes for predicting the bending strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static bending stiffness and bending strength of 105 boards of Norway spruce of dimensions 45×145×3600 mm. It is shown that Eb,1, (MOE based on the eigenfrequency of the first bending mode) gives a higher coefficient of determination to the bending strength than what Ea,1 (MOE based on the first axial eigenfrequency) does. It is also shown that eigenfrequencies corresponding to higher bending modes can be used in the definition of a new prediction variable, the modulus of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured eigenfrequencies and the expected (assuming homogeneity) eigenfrequencies of a board. The results show that using the MOI as a third prediction variable, in addition to Eb,1 and density, increases the coefficient of determination with respect to bending strength from R2 = 0.69 to R2 = 0.75.

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    FULLTEXT01
  • 52.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    SP Technical Research Institute of Sweden, Videum Science Park, 351 96, Växjö, Sweden.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Prediction of timber bending strength on basis of bending stiffness and material homogeneity assessed from dynamic excitation2012In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, no 4, p. 667-683Article in journal (Refereed)
    Abstract [en]

    The potential of utilizing resonance frequencies corresponding to edgewise bending modes for predicting the bending strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static bending stiffness and bending strength of 105 boards of Norway spruce of dimensions 45×145×3600 mm. It is shown that Eb,1, (MOE based on the resonance frequency of the first bending mode) gives a higher coefficient of determination to the bending strength than what Ea,1 (MOE based on the first axial resonance frequency) does. It is also shown that resonance frequencies corresponding to higher bending modes can be used in the definition of a new indicating property, the measure of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured resonance frequencies and the expected (assuming homogeneity) resonance frequencies of a board. The results show that using the MOI as a third indicating property, in addition to Eb,1 and density, increases the coefficient of determination with respect to bending strength from R2=0.69 to R2=0.75.

  • 53.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Marie
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Prediction of timber bending strength using dynamic excitation of bending modes2010In: Proceedings of the 11th World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Conference paper (Refereed)
    Abstract [en]

    The potential of utilizing eigenfrequencies corresponding to edgewise bending modes for predicting the bending strength of timber is investigated. The research includes measurements of axial and transversal resonance frequencies, laboratory assessment of density, static bending stiffness and bending strength of 105 boards of Norway spruce of dimensions 45×145×3600 mm. It is shown that Eb,1, (MOE based on the eigenfrequency of the first bending mode) gives a higher coefficient of determination to the bending strength than what Ea,1 (MOE based on the first axial eigenfrequency) does. It is also shown that eigenfrequencies corresponding to higher bending modes can be used in the definition of a new prediction variable, the modulus of inhomogeneity (MOI). This is a scalar value representing the lack of fit between the true, measured eigenfrequencies and the expected (assuming homogeneity) eigenfrequencies of a board. The results show that using the MOI as a third prediction variable, in addition to Eb,1 and density, increases the coefficient of determination with respect to bending strength from R2 = 0.69 to R2 = 0.75.

    Download full text (pdf)
    FULLTEXT01
  • 54.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology. SP Technical Research Institute of Sweden.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Prediction of timber bending strength and in-member cross-sectional stiffness vartiation on basis of local wood fibre orientation2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 3, p. 319-333Article in journal (Refereed)
    Abstract [en]

    Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3600 mm, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.

  • 55.
    Olsson, Anders
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Förfarande och anordning för utvärdering av en bräda av trä2014Patent (Other (popular science, discussion, etc.))
    Abstract [sv]

    Föreliggande redogörelse avser en metod och en anordning för utvärdering av en bräda av trä med en ländriktning. Data som indikerar fiberorienteringen över brädans yta inhämtas och för ett antal underpartier hos brädan bestäms en nominell, lokal elasticitetsmodul, MOE, på basis av nämnda fiberorienteringsdata och en nominell materialparameter. En nominell global MOE i längdriktningen för träbrädan i sin helhet genereras och jämförs med en sekundär global MOE. På basis av nämnda fiberorienteringsdata och denna jämförelse genereras en uppskattad lokal elasticitetsmodul, MOE, i nämnda längdriktning för ett flertal underpartier. Dessa data kan användas för exempelvis tillförlitlig hållfasthetsgradering av träbrädor.

  • 56.
    Ormarsson, Sigurdur
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vessby, Johan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Filchev, Ivan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Numerical analysis of failure modes and force distribution in a pitched roof structure of wood2016In: Proceedings of the 2016 World Conference on Timber Engineering (WCTE) / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Conference paper (Refereed)
    Abstract [en]

    Instability failures of timber elements and timber structures are reported relatively frequently although there are some suggestions available how to prevent such failures. These types of failures are characterized by sudden deformations that typically lead to failure in a single loadbearing element or collapse of the entire structure. This paper deals with buckling analysis and geometric nonlinear stress analysis of pitched roof structures of wood. A FE- model has been developed and used to study how different parameters influence the buckling modes and force distribution in the lateral bracing system of the roof structure. The simulated forces in the bracing system are also compared with results based on a simple design method given in Eurocode 5 (EC5) and a method where the compressed top chord is treated as a beam on a continuous elastic foundation. The buckling simulations showed the out-of-plane buckling to be the critical failure mode for the truss structure studied and the geometric nonlinear analysis showed the bracing stiffness and the bracing forces to be significant lower than those calculated by hand according to EC5.

  • 57.
    Petersson, Hans
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bengtsson, Tomas
    Blixt, Johan
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Källsner, Bo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sterley, Magdalena
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Oscarsson, Jan
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Högre värdeutbyte genom våt- och torrlimning av sågade sidobrädor till egenskapsoptimerade träprodukter för byggmarknaden2009Report (Other (popular science, discussion, etc.))
    Abstract [en]

    The purpose of this project was to investigate the possibilities to manufacture wet-glued laminated beams for load bearing applications from Norway spruce side board lamellae and by that achieve products that are difficult to obtain from the centre yield of a log and also contribute to increased profitability in the sawmill industry.

     

    Properties such as shape stability, strength and stiffness of wet glued beams with crosssectional dimensions 50×300 mm2 and lengths 4850 and 5200 mm were analysed and compared with corresponding dry glued products. The results obtained are very promising. espite the fact that the beams were produced from a batch of unsorted boards, the performed tests showed that the product has the necessary qualities to be competitive in relation to both glued laminated timber of grade L40 and structural strength graded timber of grade C35. Requirements concerning limitations for geometrical characteristics as expressed in a proposal for a new harmonised glulam standard are also met.

     

    The bond line of the wet glued beams was analysed regarding mechanical properties such as fracture energy, local strength and wood failure percentage after cyclic boiling and drying treatments. The results showed that the bonds are able to comply with requirements concerning bond lines to be used in indoor as well as outdoor constructions for structural pplications.

     

    To be able to improve the quality of boards for use as lamellae in wet glued beams, a method for scanning the slope of grain and disturbance of grain on board surfaces was also further developed and implemented.

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    TD-Reports_no_53
  • 58. Petersson, Hans
    et al.
    Källsner, Bo
    Ormarsson, Sigurdur
    Shape stability of laminated planks made of green-glued pairs of side boards2005In: COST Action E34: International Conference/workshop of green gluing of wood – process – products - market, Borås: SP Swedish National Testing and Research Institute , 2005Conference paper (Refereed)
  • 59.
    Petersson, Hans
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Ormarsson, Sigurdur
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Strength grading of structural timber based on buckling analysis and scanning techniques2016In: Proceedings of the 2016 World Conference on Timber Engineering (WCTE) / [ed] J. Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Conference paper (Refereed)
    Abstract [en]

    This paper assesses the potential of grading of structural timber by use of in-plane buckling analysis combined with scanning, employing post processing of both ordinary photo images and images of wood surfaces illuminated by a large number of laser point sources. The results appear very promising in providing accurate predictions of structural strength. Finite element modelling is applied in the buckling analysis and obtained results are compared with experimental results from timber boards tested in accordance to the European standard EN 408 by four point bending tests.

  • 60.
    Petersson, Hans
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Ormarsson, Sigurdur
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vessby, Johan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Influence of structural stability and material property variations on bending strength of solid timber2015In: Theoretical, Numerical, and Experimental Analyses in Wood Mechanics, 2015Conference paper (Refereed)
  • 61.
    Sejkot, Petr
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Klokner Inst, Czech Republic.
    Ormarsson, Sigurdur
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vessby, Johan
    Karlstads University, Sweden.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Numerical out-of-plane stability analysis of long span timber trusses with focus on buckling length calculations2020In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 204, p. 1-10, article id 109670Article in journal (Refereed)
    Abstract [en]

    According to the harmonized European design code for timber structures, Eurocode 5, all pitched timber trusses are designed as an in-plane structure, meaning that the bracing systems used are assumed to prevent the out-of-plane failure of the truss if sufficient strength and stiffness are provided. The present paper studies how the stiffness of a wooden bracing system contributes to the out-of-plane stability of a trussed roof structure. Results from numerical simulations indicate that significant bracing forces may occur in compressed structural members for long-span timber structures. As well, the values obtained from the calculations according to Eurocode 5 are occasionally far from the results obtained by numerical simulations.

  • 62.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Blixt, Johan
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sterley, Magdalena
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Petersson, Hans
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Wet glued laminated beams using side boards of Norway spruce2011Report (Other academic)
    Abstract [en]

    In a previous research project, carried out during the years 2006-2008, the possibility to manufacture wet glued laminated beams using ungraded laminations of Norway spruce side boards was investigated with very promising results.

    In the project presented in this report, the performance of the wet glued beams has been further investigated and developed as regards grading of side board laminations, bond line properties and lamination finger jointing. The possibility to use scanning equipment for measurement of fibre angles and prediction of strength and stiffness of boards and beams has been studied and the procedures for technical approval and CE marking have been probed into. Studies concerning market and economy for the beams and layouts for a pilot plant and a full capacity plant, respectively, for production of such beams have also been carried out.

    The possibility to grade side boards in the wet state using axial dynamic excitation was investigated with a positive result. From such excitation, a board’s stiffness (modulus of elasticity) could be determined. Accordingly, grading criteria regarding axial stiffness, and knot size, was applied to grade side board laminations into two classes; outer and inner laminations. Strength and stiffness tests of beams manufactured from such graded laminations showed that the beams actually could challenge first rate glulam and LVL products available on the market.

    Regarding beam shape and shape stability, cross section cupping may need further attention. Even if this deformation was small, it was still visible to the naked eye. The problem could probably be overcome if the beams are dried to a moisture content of 12-14% before planing.

    Results of shear tests show that green glued bond lines can fulfil strength requirements for glulam. However, delamination requirements for service class 3 (outdoors) were not fully met. From small scale tensile testing of glued bonds it was concluded that green glued bonds with high density wood have the same tensile strength and fracture energy as dry glued bonds. For bonds with low density wood and/or small amount of adhesive, the tensile strength could be lower than for dry glued bonds, whereas the fracture energy was on a similar level.

    Strength testing of wet and dry glued finger joints demonstrated that joints glued from high density wood was significantly stronger than low density joints and that there was no significant difference between the strength of green glued joints and joints glued after drying. From X-ray measurement it was shown that the glue penetration into the wood fibres is much deeper in a green glued joint than in a joint that is glued in the dried state.

    From scanning algorithms developed within the scope of this project it is possible to obtain reasonably accurate predictions of grain-angle distributions on board surfaces as well as rather accurate descriptions of knot locations and of fibre-angle disturbances around knots. From scanning of board ends, cross section characteristics with respect to radial and tangential directions and of annual ring widths could also be determined. Finally, both board and beam stiffness were predicted from this data, with an accuracy that is comparable with the one obtained from well-reputed commercial grading systems.

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  • 63.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Oscarsson, Jan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Enquist, Bertil
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sterley, Magdalena
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Petersson, Hans
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Green-glued laminated beams: High performance and added value2010In: World Conference on Timber Engineering, 2010Conference paper (Refereed)
    Abstract [en]

    The work presented in this paper deals with the use of green gluing (also known as wet gluing) as a mean to overcome the difficulties in making use of side boards for structural applications. By manufacturing laminated beams from unseasoned side boards several advantages are obtained. Beams were manufactured from side boards of approximately 25 mm thickness. The board width was 120 mm. The boards were glued together with a 1-component polyurethane adhesive to form a beam cross-section of approximately 120×315 mm2. After curing, the beams were split into two halves, each approximately 55 mm wide. These 55×315 mm2 beams were then dried in a conventional kiln dryer. Finally, the beams were planed to target size, 50×300 mm2. Tests performed included beam bending tests for strength and stiffness, tests of the shape stability of the beams, tests of the integrity of the adhesive bond lines (delamination) and tests on the strength and fracture energy of the adhesive bond lines. The main results obtained show that there is a potential for the production of green-glued laminated beams with good technical performance.

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    FULLTEXT01
  • 64.
    Serrano, Erik
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Vessby, Johan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Girhammar, Ulf Arne
    Luleå Tekniska Universitet.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Design of Bottom Rails in Partially Anchored Shear Walls Using Fracture Mechanics2011In: Proc. CIB-W18, Meeting 44, Alghero, Italy / [ed] Blass, 2011Conference paper (Other academic)
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    fulltext
  • 65.
    Säll, Harald
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Skog och trä.
    Källsner, Bo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Skog och trä.
    Olsson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Bending strength and stiffness of aspen sawn timber2007In: Quality Control for Wood and Wood Products, COST, Warsaw , 2007, p. 6-Conference paper (Refereed)
    Abstract [en]

    In order to investigate the possibility of using sawn timber of European aspen (Populus tremula L.) as a structural

    material, 150 pieces of the dimension 45 x 120 mm2 were selected from a sawmill in the south of Sweden. The material was

    visually strength graded using the Nordic standard INSTA 142 and the British standard BS 4978-1996, respectively.

    The timber pieces were also subjected to flat-wise bending in a Cook-Bolinder Ò strength grading machine. Finally all

    specimens were tested in edge-wise bending according to the European testing standard EN 408. Global and local moduli

    of elasticity as well as bending strength were determined.

    The results indicate that the visual grading rules, intended for use on Norway spruce and Scots pine, seem to work fairly

    well on European aspen. However, grading in a flat-wise bending machine like the Cook-Bolinder seems to give a lower

    correlation between stiffness and strength for aspen timber than generally found for coniferous. Further, the correlation

    between density and bending strength was found to be very low for the aspen timber tested. It was also noticed that

    the aspen timber has a slightly higher bending strength and modulus of elasticity than is the case for normal qualities

    of Norway spruce.

    The study indicates that sawn timber of European aspen grown in southern Sweden can be visually graded and used

    as structural material.

  • 66.
    Vessby, Johan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Directional dependency in an OSB sheathing-to-framing mechanical connection2014Conference paper (Refereed)
    Abstract [en]

    Nailed connections are commonly employed for connecting sheathings to the framing used in shear walls. Although many aspects of such connections have been investigated thoroughly within the research community generally, the effect the loading direction has on connections of this sort has been much less investigated. In the present study experimental tests were carried out for determining in detail the effects the loading has on different sheathing-to-framing connections. The results obtained indicated the degree of loading to which a nail fastened to an oriented strand board (OSB) sheathing is subjected to not be strongly affected by which of the two main loading directions is involved, but that the effects of loading direction are found to be much greater if the timber element in question is also included in the testing carried out. The dependency of the loading effect on the loading direction at different loading stages and for different directions - parallel to the fibres, perpendicular to them, at some angle between these two main directions - was investigated here.

  • 67.
    Vessby, Johan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Girhammar, Ulf Arne
    Umeå universitet, Institutionen för tillämpad fysik och elektronik.
    Influence of contact stress between sheets on strength and stiffness of timber frame shear walls2010In: Proceedings of the 11th World Conference on Timber Engineering / [ed] Ario Ceccotti, 2010Conference paper (Refereed)
    Download full text (pdf)
    FULLTEXT01
  • 68.
    Vessby, Johan
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Källsner, Bo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Olsson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Influence of initial gap between timber members on stiffness and capacity of shear walls2008In: 10:th World Conference on Timber Engineering, 2008Conference paper (Refereed)
  • 69.
    Vessby, Johan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Girhammar, Ulf Arne
    Luleå Univ Technol.
    Evaluation of softening behaviour of timber light-frame walls subjected to in-plane forces using simple FE models2014In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 81, p. 464-479Article in journal (Refereed)
    Abstract [en]

    The present investigation focuses on evaluating the entire load displacement relationship, especially the softening part, of light-frame wall segments subjected to in-plane monotonic forces when the load-slip curves of the individual sheathing-to-framing fasteners are considered. Different sheathing-to-framing joint characteristics, including unloading behaviour, and stud-to-rail joint characteristics are incorporated in the analyses. Two loading cases are investigated: Horizontal loading resulting in uplift of the leading stud and diagonal loading representing a fully anchored wall. Two common types of finite element (FE) models for the sheathing-to-framing joints are used for the analyses: A single spring model and a spring pair model, where the joint characteristics valid for the timber properties perpendicular and parallel to the grain are used. The maximum capacity of the wall segments is somewhat overestimated when using the spring pair model compared to that of the single spring model. The softening parts of the load displacement curves are significantly affected, regardless of whether the perpendicular or parallel characteristics of the joints are used. The results from FE simulations using models with perpendicular and parallel characteristics are compared with full scale test results for walls with a single segment loaded horizontally and diagonally. The behaviour of the wall segments subjected to horizontal loading is dominated by fastener displacements perpendicular to the bottom rail. Hence, FE models including perpendicular characteristics should be used. For diagonal loading the behaviour of the wall segments is dominated by displacements parallel to the framing members, and FE models including parallel characteristics should therefore be used. The analyses were extended to multiple segment walls resulting in the same type of behaviour as single segment walls. (C) 2014 Elsevier Ltd. All rights reserved.

  • 70.
    Vessby, Johan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Ormarsson, Sigurdur
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Stabilisering av takkonstruktioner i trä: arbetet med ny handbok2016In: Bygg & teknik, ISSN 0281-658X, no 4, p. 60-63Article in journal (Other (popular science, discussion, etc.))
  • 71.
    Vessby, Johan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Serrano, Erik
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Olsson, Anders
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Girhammar, Ulf Arne
    Luleå University of Technology.
    Källsner, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Simulation of bottom rail fracture in partially anchored shear walls using XFEM2012In: INTERNATIONAL COUNCIL FOR RESEARCH AND INNOVATIONIN BUILDING AND CONSTRUCTION, WORKING COMMISSION W18 - TIMBER STRUCTURES (CIB-W18): Meeting forty-five, Växjö, Sweden, August 2012, 2012Conference paper (Refereed)
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